Dental instrument.



No. 651,922.. Patented June 19,1900. w. E. HARPER.

DENTAL INSTRUMENT.

(Application filed Dec. 18, 1899.)

(No Model.)

UNITED STATES PATENT OFFICE.

\VILLIAM E. HARPER, OF CHICAGO, ILLINOIS.

DENTAL INSTRUMENT.

SPECIFICATION forming part of Letters Patent No. 651,922, dated June 19, 1900. Application filed December 18, 1899. Serial No. 74Q,751. (N0 model.)

To all whmn it may concern.-

Be it known that I, WILLIAM E. HARPER, a citizen of the United States, residing at No. 3441 Wabash avenue, Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Dental Instruments, of which the following is a specification.

This invention relates to improvements in that class of dental instruments in which a rotary tool, technically called a bur, is detachably secured in an angular head in which is appropriately journaled a shaft or shafts by means of which rotary motion is imparted to the tool from a flexible shaft in any suitable manner, the angular head being screw-threaded or otherwise attached to a handpiece or handle by which the instrument is manipulated. Numerous examples of dental instruments of this general class are found in the prior art, in many of which the angle of the axis of the tool may be adj usted and set with relation to the axis of the handle for facilitating operation upon dilferent kinds, locations, and parts of tooth-cavities; but the particular kind of head to which my invention is more particularly applicable is the right-angled head with adjustability, such heads being now commonly sold upon the market. Such heads generally consist of a right-angled casing, like the elbow of a Stovepipe, the driving-shaft being journaled in one branch of the casing and the rotary tool being appropriately journaled in the.

other section, with suitable beveled gears connecting the two shafts. Such heads are now generally screwed into a straight handle, through which extends a shaft communicating power from a flexible shaft to the tooldriving shaft. The objection to all of such instruments, whetherof the fixed right-angular type or of the adjustable angular type, is that while the axes of the handle and tool are in the same vertical plane they are in widely-different horizontal planes and are therefore very unstable, and especially in applying pressure to the rotary cutting-tool through the handle either axially or laterally, there being constant liability of the instrument canting, wabbling, or rocking about upon the bur as a pivot, and as the bur must necessarily rotate at a high speed the danger incident to operating adjacent to a thin wall or upon side walls and the difficulty of holding the tool properly to its work as against wabbling and jumping from point to point in the cavity will be readily appreciated.

The primary object of my invention is to avoid all of these difficulties by having the pressure applied to the cutting-tool or .bur in a plane substantially coincident with the cutting edge of the bur.

Another object is to have the axis of the handle oblique to the axis of the cutting-tool and so disposed as to intersect the axis of the cutting-tool substantially at the cutting edge or point thereof, whereby all tendency to instability, lateral canting, or wabbling of the tool is'avoided.

A further object is to have the handle of simple and novel construction, combining strength and rigidity in the maximum degree, and yet so constructed as to afiord proper bearings for the angular transmission of power therethrough, to afford ready access to the transmittinggears both in assembling and separating the. parts, and so as to afford a cheap construction permitting the proper boring and dressing of the angularly-disposed bearings and faces for the gearing while the tool is straight and prior to its being bent to the angular form necessary to bring its axis to a line that will intersect the 'axis of the cutting-tool substantially at the cutting edge or point of the tool.

These and such other objects as may hereinafter appear are attained by the devices illustrated in the accompanying drawings.

Figure 1 is a side elevation, partly broken away, of a dental instrument embodying my invention. Fig. 2 is a diagrammatic elevation thereof. Fig. 3 is an inverted plan view of the same, and Fig. 4 is a perspective view of the cap covering the gear-chamber inthe as at B, is screwed or otherwise secured the handle 0, and in the other end of which is suitably journaled' the cutting-tool D, which,

as usual, is detachable from the head for'in-V terchangeability from other tools havingdifferentlyl-shaped cutting points or edges, the cutting-tool being usually connected by abeveled gear with a short shaft (not shown) journaled in the other section of the head, which is in turn detachably coupled to the tool-. driving-shaft E. I have not deemed it necessary to illustrate or describe in detail the construction of this head, because it is identical with those now generally found upon the market and iswell understood by those a screw. The angle between the parts F and G of the handle is intended to be such that the axis of the handle (represented by the dotted lines H H in Fig. 2) is oblique to the axisof the cutting-tool or bur D and is so disposed with relation thereto as to intersect theaxis of said tool substantially at the cutting edge or point thereof. When so disposed, the plane of pressure applied to the. .handle is substantially coincident with the plane of the cutting edge or point of the tool, and hence when pressure is applied in a direction substantially parallel with the axis ofthe cutting-tool there will be no tendency whatever to instability, wabbling, or canting of the tool, and this tendency is reduced to the minimum when pressure is-applied laterally.

of the tool-as, for instance, in working on the side wall of a cavity-for the point of re-' sistance will be coincident with the plane of pressure. This general featureof construction. is of the utmost importance, because itenables the manipulation of the instrument with great delicacy and accuracy, as well as with great power, notwithstanding the high speed at which the cutting-tool is rotating and regardless of whether the work is being done upon a surface. at right angles to orsubstantially parallel with the axis of the cutting-tool, for with'the liability to cant and wabble when pressure is applied the operator need trust to himself only to the'proper placing ofthe t0ol,while being free to apply;

such pressure as may be needed in suchdirection as it may be needed. This would not be true. were theaxis of the handle at right angles to the axis of the cutting-tool or at any 7 other angle thereto without intersecting the axisof the cutting-tool substantially; at the pointer cutting edge thereof. This'advantageisof especial importance in operating; 1,

against .or adjacent to very .thin walls,where .it commercially impracticable.

pressure} towhichit a slight motion,unexpected or uncontrollable,

of a very small fraction of an inch would break down the wall and cause excruciating pain and possibly serious and. lasting consequences to the patient. The construction of the handle is also novel and greatly reduces the cost of the instrumentin that instead of having the handle cast in the shape shown in the drawings I propose to have it formed in the first instance of a straight tubular blank, so that a single tool can be used for V drilling the bearings for the tool-drivin g shaft E as well as the seat for the bushing I of the handle-shaft J and at the same time provide ready access to the gear-cavity K for dressing the face thereof opposing the backs of the first instance with the solid central portion from which is formed by. milling the two diaphragms L and M, affording bearings for the shafts E and J, said diaphragms, being suitably distanced apart. While the blank is still straight, the wall thereof at one. side is milled out, as shown more clearly in Fig. 3, substantially half of-the circumference thereof between the diaphragms, which so weakens the casing at this point, that it may be bent to the form shown without disturbing the proper alinement of the bearings in gears. This handle.is-formedstraightin the the diaphragms L and M for the shafts E and J. The spacebetween the diaphragms constitutes the gear-chamber K, and the opening formed by milling out the side thereof affords a ready means of access to the chamher to facilitate the securing of the angularlydisposed gears N and 0 upon the shafts E. and J, respectively. The opening caused by milling away the wall of. they gear-cavity,.

as before explained, is. closedby a. cap P,

(shown in detail in Fig. 4,). which cap is secured in place by screws and is. so shaped as to give a smooth finishto thehandle. Obviously if the handle. were cast in the-shape shown it would involve considerably more ex pense to drill the bearings for the. shaftsE .and J, which would have to be. done upon two different, angles and in two. difierent opera-- tions, besides which considerable difiiculty would be encountered in such angular drilling in having the p'roper.intersection. be

ICC

tween the axis of the shaft so that the gears would work smoothly and freely,.and such difficulties, I have foundby e2-:perien ce'wouldv so increase the cost. of the handleas to make While themilling-out of the side of tnl handle weakens, it, in comparison with theend portions of the handle,- to such an extent as toinsure the properbending taking. place at the proper point in thev handle, still'suchcutout portion does not affect-the rigidity ofthe handle in operation, for ample stockis leftto' insure that the bent handle will resist any may everbe. subjected in use.

WhileI ita the'angular ihandleof the l general form and construction herein. shown and described, I do not desire to limit myself to the same, for so far as relates to the broad idea of my invention the shape and construction of the handle, as well as of the tool-carrying head, is immaterial so long as the axis of the handpiece of the handle, to which pressure is primarily applied, is oblique to the axis of the tool and intersects the same snbstantially at the cutting edge or point thereof, for it is within the contemplation of my invention that the sections F and G of the handle may be separable from one another and the section G, comprising the angular portion of the handle, may be formed with or attached to the head, leaving the handle proper or the handpiece straight. The fixed right-angled head illustrated in the drawings in conjunction with the angular handle produces an exceptionally-handy instrument, which is simple, cheap, and compact and not liable to get out of order; but it is obvious that a multangular head may be used either with the angular handle shown or with a straight handle so disposed that the axis thereof shall have the same relation to the axis of the cutting-tool as that shown in the instrument herein illustrated and described.

Having thus fully described my invention,

What I claim, and desire to secure by Letters Patent, is

1. In a dental instrument, the combination with ahead and a rotary cutting-tool mounted therein, of a handpiece therefor said head and cutting-tool being disposed in a plane at an angle to the axis of the handpiece and a rotary shaft in said handpiece operatively connected with said tool, the axis of said handpiece being so disposed as to intersect the axis of the cutting-tool substantially at the cutting edge or point thereof, substantially as described.

2. In a dental instrument, the combination with an angular head and a rotary cutting tool mounted therein, of an angular handle and a shaft journaled therein and operatively connected with the cutting-tool, the axis of the handpiece of said handle being disposed oblique to the axis of the cutting tool so as to intersect the same substantially at the cutting edge or point of the tool, substantially as described.

3. In a dental instrument, the combination with an angular head and a rotary cuttingtool mounted therein, of an angular handle having a gear-chamber substantially at the juncture of its angular portions, bearings at either side of said chamber, shafts journaled in said bearings and gears connecting said shafts, one of said shafts being operatively connected with the rotary cutting-tool and the other of said shafts constituting a driv ing-shaft, substantially as described.

4:. As a new article of manufacture, a handle for dental instruments comprising an an gular metallic tube cut away at the bend thereof and provided with a gear-chamber, a removable cap for said chamber, bearings on opposite sides of said chamber, shafts jour naled in said bearings and gears connecting said shafts, substantially as described.

- WILLIAM E. HARPER.

Witnesses:

O. L. Woon, M. E. SHIELDS. 

